Active cargo transport with Janus colloidal shuttles using electric and magnetic fields

Abstract

Active colloids show non-equilibrium behavior that departs from classical Brownian motion, thus providing a platform for novel fundamental phenomena and for enticing possible applications ranging from water treatment to medicine and microrobotics. Although the physics, motion mechanisms and guidance have been extensively investigated, active colloids are rarely exploited to simultaneously guide and transport micron-sized objects in a controllable and reversible manner. Here, we use autonomous active Janus particles as colloidal shuttles to controllably transport cargo at the microscale using external electric and magnetic fields. The active motion arises from the metallodielectric characteristics of the Janus particles, which allows them to also trap, transport and release cargo particles through dielectrophoretic interactions induced by an AC electric field. The ferromagnetic nature of the nickel layer that forms the metallic hemisphere of the Janus colloids provides an additional mechanism to direct the motion of the shuttle using an external magnetic field. With this highly programmable colloidal system, we are able to harness active colloid motion and use it to transport cargo particles to specific destinations through a pre-defined route. A simple analytical model is derived to successfully describe the motion of the shuttle-cargo assembly in response to the applied electrical field. The high level of control on cargo pick-up, transport and release leads to a powerful delivery tool, which could eventually be used in microactuators, microfluidics or for controlled delivery within organ-on-a-chip devices.

Review: Interactions of Active Colloids with Passive Tracers

“…Different from micromotors that are based on self-electrophoresis, under an external alternating current (AC) electric field, metallodielectric Janus particles can realize self-propulsion with two mechanisms: induced charge electrophoresis (ICEP) [54][55][56] and self-dielectrophoresis (sDEP) [55][56][57] altered by the frequency of the electric field. At low frequencies, an asymmetric induced-charge electroosmotic flow (induced by different polarizabilities of two hemispheres) leads to motion in the direction of the dielectric side (ICEP) [54][55][56].…”

Active particles in geometrically confined viscoelastic fluids

“…acoustic [13], magnetic [14] and optical fields [15]. Understanding the behavior of these artificial agents in realistic complex environments is of great significance [16], since they can be employed in many biomedical applications such as drug delivery [17], cargo transport [18,19], bio-sensing [20] etc. Besides, an active particle (AP) in a viscoelastic fluid represents an example of a random walker in a nonequilibrium thermal bath, being of fundamental relevance for non-equilibrium statistical physics [21].…”

Interactions of Different Janus Particles with Passive Tracers

“…Here, the interactions are due to dielectricphoretic interplays induced by the different polarizability compared to medium. [14,15,16,17,18] Here, not only a strong dependence on the frequency was observed [19], but also the crucial importance of the material combinations, compare [15] and [16]. For light driven systems even a certain tuneability by variation of fuel and light wavelength has been reported.…”